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I/O List
If the I/O port (3n-1) returns 0, card is not there.
I/O port (3n-1) returns the card type.
Top 4 bits mean the card genre:
0x0: Video
0x1: Audio
0x2: System
Bottom 4 bits mean the card type:
Video:
0x1: Video Mark I
0x2: Video Mark II
Audio:
0x1: Sound Mark I
System:
0x1: Math Mark I
0x2: Text Mark I
0x3: Debug
0x4: ROMcard Mark I
Video Mark I card maps itself to:
+0: VDP address
+1: VDP data
+2: See above
Video Mark II card maps itself to:
+0: VDG VRAM address
+1: VDG VRAM data
+2: See above
Sound Mark I card maps itself to:
+0: PSG address
+1: PSG data
+2: See above
Math Mark I card maps itself to:
+0: AM9511 stack
+1: AM9511 command (W) / AM9511 ready (R)
+2: See above
Text Mark I card maps itself to:
+0: Keyboard data
+1: Empty
+2: See above
Debug card maps itself to:
+0: Address
+1: LED
Bit to 7-segment map:
0
1 2
3
4 5
6 7
+2: See above
ROMcard Mark I card maps itself to:
+0: Address (Holds 24 bit address inside, gets left shifted by each write)
+1: Data
+2: See above